1. Field of the Invention
This invention relates to a one step process for imparting both fire retardancy and resistance to wood destroying organisms to products composed primarily of perishable cellulosic materials, particularly those having wood as a major component of the product. The principal utility of the invention will be practiced by industries producing wood roofing materials, decks, foundations, poles, and industrial construction materials. However, the invention may provide the decay resistant and fire retardant benefits to a large variety of other products for use in settings other than those mentioned.
2. Description of the Prior Art
Wood products have been treated with both a variety of chemicals and treatment methods to attempt to achieve the desired levels of effectiveness for both fire retardancy and decay resistance. Present methods have focused on initially treating the wood for either fire retardancy or decay resistance, followed by a drying phase, and a second treatment for the remaining desired characteristic. However, those methods have not been entirely satisfactory for a variety of reasons, such as the extra energy and handling associated with the drying phase, insufficient penetration of the second treatment due to the spaces in the wood product being filled to capacity with the first treatment, and less than satisfactory levels of effectiveness for one or both of the desired characteristics.
The prior art is basically divided into fire retardant compounds and systems and decay compounds and systems.
It has long been known that certain compounds will impart decay resistance to wood products. Examples of compounds known to have decay resistant qualities include oil-borne preservatives such as creosote and pentachlorophenol, tertiary and quaternary ammonium compounds, didecyl dimethyl ammonium chloride, some heavy metals, such as copper and zinc, and certain compounds containing boron.
It has also been known that certain compounds will impart fire retardant qualities to wood products. Examples of compounds known to have fire retardant qualities include mixtures containing a combination of dicyandiamide, formaldehyde, and phosphorus (often in the form of phosphoric acid) and sometimes urea or melamine.
The first group of patents listed all generally pertain to fire retardant compositions, methods related to imparting fire resistance to wood products, and products resulting from the use of either or both the composition and the methods.
______________________________________ U.S. Pat. No. Inventor ______________________________________ 2,295,504 R. S. Shelton 2,694,663 R. D. Stayner 2,917,408 I. S. Goldstein et al. 3,159,503 I. S. Goldstein et al. 3,832,316 S. C. Juneja 3,836,669 Z. A. Dadekian 3,887,511 S. C. Juneja 3,925,137 M. Kamei 3,986,881 W. J. Oberley 4,010,296 W. J. Oberley 4,123,575 L. Wesch et al. 4,254,177 G. E. Fulmer 4,273,687 R. W. Cummins et al. 4,444,790 H. A. Green 4,461,720 A. G. Loyvet et al. ______________________________________
U.S. Pat. No. 2,917,408 is primarily directed to a method for impregnating wood for flame retardance and stabilization against dimensional change with a specified solution of dicyandiamide, phosphoric acid, and water followed by a heat treatment. A further aspect of the invention relates to the addition of certain zinc or copper compounds for enhanced resistance to fungal decay.
U.S. Pat. No. 3,159,503 relates to the chemical treatment of wood with a solution of dicyandiamide, phosphoric acid, formaldehyde, and water followed by a heat treatment. That treatment involves an impregnation technique which renders the wood fire retardant, stabilized against dimensional change, and reduces its hygroscopicity. This patent is also directed to a leach-resistant, fire retardant product and a method for producing that product.
U.S. Pat. No. 3,832,316 is directed to resin solutions primarily of melamine, dicyandiamide, formaldehyde, and an oxy-acid of phosphorus which are suitable for fire retardant and adhesive applications.
U.S. Pat. No. 3,887,511 is concerned with aqueous solutions, and methods for preparing the same, of incompletely reacted urea compounds, dicyandiamide, formaldehyde, and an oxy-acid of phosphorus to render wood and cellulosic products fire retardant and decay resistant.
U.S. Pat. No. 3,925,137 relates to a method for forming a flame retardant clear coat which is accomplished by first applying a flame retardant foaming paint, then attaching a decorative material, and lastly a flame retardant clear coat. The compositions for the foaming paint and the clear coat are taught.
U.S. Pat. No. 3,986,881 discloses wood treatment chemical compositions, both aqueous and solid, of monomethylol dicyandiamide, melamine, and phosphoric acid which impart fire retardant qualities as well as leach resistance and do not increase the hygroscopicity of the wood.
U.S. Pat. No. 4,010,296, a divisional of Patent No. 3,986,881, is directed to methods of treating wood for imparting desirable properties related to low hygroscopicity, leach resistance, and fire retardance.
U.S. Pat. No. 4,123,575 relates to a fire retarding, foam-forming epoxy resin and a method for applying the same.
U.S. Pat. No. 4,254,177 is directed to articles having fire retardant qualities. The articles have a foraminous core and an adherent outer layer containing fire retardant fillers.
U.S. Pat. No. 4,273,687 relates to a guanidine phosphate composition which renders cellulosic materials, such as hardboard, fire retardant.
U.S. Pat. No. 4,461,720 discloses a fire retardant composition for treating wood prepared by converting dicyandiamide, through a series of steps, into phosphate salt of the methylolated guanyl urea.
The second group of patents all generally pertain to compositions and methods related to imparting decay resistance or displaying biocide action to wood products. Following is a list of related prior art patents.
______________________________________ U.S. Pat. No. Inventor ______________________________________ 2,294,504 R. S. Shelton 2,694,663 R. D. Stayner 3,836,669 Z. A. Dadekian 4,444,790 H. A. Green 4,950,685 H. A. Ward ______________________________________
U.S. Pat. No. 2,295,504 is directed to a compound or compounds of the class of tertiary and quaternary ammonium compounds which possess bactericidal, antiseptic, fungicidal, and related germ counteracting properties.
U.S. Pat. No. 2,694,663 discloses a composition for the control of micro-organisms comprising a quaternary ammonium germicide and a neutral hydrocarbon oil promoter.
U.S. Pat. No. 3,836,669 teaches a method involving the use of didecyl dimethyl ammonium chloride for the purpose of killing bacteria in the presence of hard water and blood serum.
U.S. Pat. No. 4,444,790 relates to the use of a quaternary ammonium compound as a disinfectant in the presence of hard water or organic soil.
U.S. Pat. No. 4,950,689 relates to the combination of didecyl dimethyl ammonium chloride with 3-iodo-2-propynyl-butyl carbamate for the purpose of providing decay resistance to wood products.